FIELD OF THE INVENTION
The invention relates to a transition element between components of a flue-gas duct disposed downstream of a gas turbine of a power station plant.
Gas turbines are used in many sectors, in particular in power station plants, for driving generators or machines. In that case, the energy content of the fuel is utilized to produce rotary movement of a turbine shaft. To that end, a working medium or hot gas resulting during the combustion of the fuel is expanded in the gas turbine and then fed as exhaust gas or flue gas to a flue-gas duct attached to the gas turbine.
The flue-gas duct of the gas turbine normally includes a plurality of components or duct pieces connected to one another. Depending on the structure and mode of application of the gas turbine, a diffuser, a compensator and/or further elements, such as, for example, a main flue and a bypass flue, are provided as the components.
Each component is normally heated during operation of the gas turbine by the exhaust gas or flue gas flowing through it. In the process, the flue gas cools down in the flue-gas direction by heat exchange with the respective components. Each component is therefore heated to a different temperature depending on its position in the flue-gas duct. Thus, structural parts which are heated to a different temperature level bear against one another in the region of the transition between two components, which leads to mechanical stresses between the components. In particular, during changes of load at the gas turbine, such as during starting operations for example, a transient temperature load may result in considerable stressing of the components of the flue-gas duct. Damage to the components of the flue-gas duct caused thereby results in a reduction in the service life of the entire gas-turbine plant, which leads to an extremely undesirable reduction in the availability of the gas-turbine plant. An exhaust collector which is known from French Published Patent Application 2 469 563, corresponding to U.S. Pat. No. 4,391,566, is connected downstream of a gas turbine and has a heat-insulation element for the insulation of installed components against flue gas heat.